湖相泥页岩储层脆性评价及影响因素分析——以苏北盆地海安凹陷曲塘次凹泥页岩为例

Evaluation and influencing factors for brittleness of lacustrine shale reservoir: a case study of Qutang Sub-Sag, Subei Basin

孙彪 刘小平 舒红林 焦创赟 王高成 刘梦才 罗瑀峰

SUN Biao LIU Xiaoping SHU Honglin JIAO Chuangyun WANG Gaocheng LIU Mengcai LUO Yufeng

油气资源与探测国家重点实验室, 北京 102249 中国石油大学(北京) 地球科学学院, 北京 102249 中国石油 浙江油田分公司, 杭州 310013 中国石油 长庆油田分公司 勘探开发研究院, 西安 710018

State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing 102249, China College of Geosciences, China University of Petroleum (Beijing), Beijing 102249, China PetroChina Zhejiang Oilfield Company, Hangzhou, Zhejiang 310013, China Petroleum Exploration and Development Research Institute, PetroChina Changqing Oilfield Company, Xi'an, Shaanxi 710018, China

为准确评价湖相泥页岩脆性及探究其影响因素，选取了苏北盆地海安凹陷曲塘次凹古近系阜宁组二段湖相泥页岩样品，利用全岩X衍射分析、有机碳测定、镜质体反射率测定、扫描电镜、三轴岩石力学等实验技术手段，分析了样品的矿物成分、地球化学、储集空间等特征；并采用测井、强度参数、矿物成分以及应力—应变曲线变化特征等方法评价其脆性特征。结果表明，页岩主要为云质页岩和灰质页岩，脆性矿物含量较高；有机碳含量平均为1.25%，且已达到成熟阶段；储集空间由特低孔和裂缝组成；应力应变关系曲线表现出较强的脆性特征；不同方法的脆性评价结果存在一定差异，基于弹性参数与矿物组分评价脆性比基于强度参数的应用效果更佳，但每种方法都存在一定局限性。阜二段页岩脆性受矿物组分、有机质丰度、储集空间发育程度等共同影响，随着白云石含量、有机质成熟度、裂缝发育程度的增加，储层脆性随之增加；而方解石含量、有机质丰度、孔隙度的增加则会减弱储层脆性。

In order to accurately evaluate the brittleness of lacustrine shale and explore its influencing factors, the mineral compositions, geochemical characteristics and reservoir spaces of the lacustrine shale samples from the second member of Paleogene Funing Formation in the Qutang Sub-Sag, Hai'an Sag, Subei Basin were analyzed by means of whole-rock diffraction analysis, the measurement of organic carbon content (TOC) and vitrinite reflectance, scanning electron microscope (SEM) and triaxial rock mechanics experiment, combining with well logging, strength parameters, mineral compositions and stress-strain curves. The shale is mainly dolomitic and calcite ones with a high content of brittle minerals. The average TOC value is 1.25%, indicating for a mature stage. The reservoir space is composed of ultra-low pores and fractures. The stress-strain curves show a strong characteristic of brittleness. The brittleness evaluation results of different methods have certain differences. The results based on elastic parameters and mineral components are more reliable than that based on strength parameters although each method has its own limitations. The mineral compositions, organic matter abundance, and the degree of storage space development affect the brittleness of shale in the second member of Funing Formation. With the increasing of dolomite content, organic maturity and fracture development, the brittleness of the reservoir increases. The increase in calcite content, organic matter abundance and porosity will weaken the brittleness of the reservoir.

国家自然科学基金项目 42072150;国家自然科学基金项目 41372144;国家科技重大专项 2017ZX05049001-008

https://doi.org/10.11781/sysydz2021061006